Brad Katsuyama says opponents are ‘mischaracterizing’ IEX’s features

WASHINGTON—IEX Group Inc., the upstart trading venue that says it wants to level the playing field between investors and high-frequency traders, is planning to fight efforts to change how it operates as it tries to become a full-fledged stock exchange, its chief executive said.

CEO Brad Katsuyama, in an interview, stood firm against calls by opponents, led by firms such as the New York Stock Exchange and Citadel LLC, to alter...